OregonFlora: Juncus confusus vs. Juncus interior

	Juncus confusus	Juncus interior
	Colorado rush	interior juncus
Habit	Plants perennial, 20–50 cm tall, cespitose, stems with 0–5 strong ridges visible on one side.	Plants perennial, (11)20–60 cm tall, cespitose, base usually pink, 4–6 strong stem ridges visible per side.
Leaves	thin and wiry; blade flat and slightly inrolled; auricles soft and thin distally, 0.3–0.8 mm; dull, rounded or acute; dirty white to translucent.	thin and wiry; blade flat and slightly inrolled; auricles soft, 2-textured, usually thicker proximally and more opaque than thin distal margin, 0.4–0.8(1.2)mm; dirty white to translucent; dull, rounded.
Inflorescences	cymes, 0.5–2.5 cm, usually dense and small.	cymes, 1.5– 7 cm; bractlets subtending flowers acuminate to aristate.
Flowers	tepals 6, with broad medium brown stripes flanking a green midvein; tepal tips acuminate; erect; equal or subequal; stamens 6; filaments 0.7–1.1 mm; anthers 0.5–0.7 mm; styles 0.05–0.2 mm.	tepals 6, light brown; tepal tips acuminate; stamens 6; filaments 0.8–1.1 mm; anthers 0.3–0.7(0.9) mm; styles 0.1–0.4(0.5)mm.
Capsules	2.5–3.5 mm; shorter than or equaling tepals, brown to dark brown; apex notched, crested, 3-chambered.	3.3–4.7 mm; longer than the tepals, light brown; apex obtuse to truncate, not ridged or crested, 1-chambered.
Seeds	0.4–0.5 × 0.2–0.3 mm, apiculate, longitudinally ridged.	0.3–0.45 × 0.15–0.25 mm, apiculate.
2n	=80.	=80.

	Juncus confusus	Juncus interior
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	Seasonally moist or wet meadows, springs, swales, shores, ditches. 800–2700 m. BR, BW, ECas, Owy, Sisk. CA, NV, ID, WA; north to British Columbia, east to SD, southeast to NM. Native. This species is often confused with Juncus occidentalis, which shares the brown-striped tepals and crested capsules but does not grow east of the Cascades. Where they overlap in southwestern Oregon and California, they are separable by the internal structure of the capsules: three-chambered in J. confusus and one-chambered in J. occidentalis.	River shores. 50–200 m. Col. CA, ID, WA; throughout North America. Native.
Source	Flora of Oregon, volume 1, page 274 Peter Zika	Flora of Oregon, volume 1, page 279 Peter Zika
Sibling taxa	J. acuminatus, J. anthelatus, J. articulatus, J. balticus, J. bolanderi, J. brevicaudatus, J. breweri, J. bryoides, J. bufonius, J. bulbosus, J. canadensis, J. capillaris, J. capitatus, J. compressus, J. conglomeratus, J. covillei, J. diffusissimus, J. drummondii, J. dudleyi, J. effusus, J. ensifolius, J. ensifolius x Juncus nevadensis, J. exiguus, J. falcatus, J. filiformis, J. gerardi, J. hemiendytus, J. hesperius, J. howellii, J. inflexus, J. interior, J. kelloggii, J. laccatus, J. lescurii, J. longistylis, J. marginatus, J. mertensianus, J. mexicanus, J. nevadensis, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. planifolius, J. ranarius, J. regelii, J. saximontanus, J. supiniformis, J. tenuis, J. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis	J. acuminatus, J. anthelatus, J. articulatus, J. balticus, J. bolanderi, J. brevicaudatus, J. breweri, J. bryoides, J. bufonius, J. bulbosus, J. canadensis, J. capillaris, J. capitatus, J. compressus, J. confusus, J. conglomeratus, J. covillei, J. diffusissimus, J. drummondii, J. dudleyi, J. effusus, J. ensifolius, J. ensifolius x Juncus nevadensis, J. exiguus, J. falcatus, J. filiformis, J. gerardi, J. hemiendytus, J. hesperius, J. howellii, J. inflexus, J. kelloggii, J. laccatus, J. lescurii, J. longistylis, J. marginatus, J. mertensianus, J. mexicanus, J. nevadensis, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. planifolius, J. ranarius, J. regelii, J. saximontanus, J. supiniformis, J. tenuis, J. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Juncus interior

Colorado rush

interior juncus

Habit

Plants perennial, 20–50 cm tall, cespitose, stems with 0–5 strong ridges visible on one side.

Plants perennial, (11)20–60 cm tall, cespitose, base usually pink, 4–6 strong stem ridges visible per side.

Leaves

thin and wiry;

blade flat and slightly inrolled;

auricles soft and thin distally, 0.3–0.8 mm; dull, rounded or acute; dirty white to translucent.

thin and wiry;

blade flat and slightly inrolled;

auricles soft, 2-textured, usually thicker proximally and more opaque than thin distal margin, 0.4–0.8(1.2)mm; dirty white to translucent; dull, rounded.

Inflorescences

cymes, 0.5–2.5 cm, usually dense and small.

cymes, 1.5– 7 cm;

bractlets subtending flowers acuminate to aristate.

Flowers

tepals 6, with broad medium brown stripes flanking a green midvein;

tepal tips acuminate; erect; equal or subequal;

stamens 6;

filaments 0.7–1.1 mm;

anthers 0.5–0.7 mm;

styles 0.05–0.2 mm.

tepals 6, light brown;

tepal tips acuminate;

stamens 6;

filaments 0.8–1.1 mm;

anthers 0.3–0.7(0.9) mm;

styles 0.1–0.4(0.5)mm.

Capsules

2.5–3.5 mm; shorter than or equaling tepals, brown to dark brown;

apex notched, crested, 3-chambered.

3.3–4.7 mm; longer than the tepals, light brown;

apex obtuse to truncate, not ridged or crested, 1-chambered.

Seeds

0.4–0.5 × 0.2–0.3 mm, apiculate, longitudinally ridged.

0.3–0.45 × 0.15–0.25 mm, apiculate.

=80.

Juncus interior

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Seasonally moist or wet meadows, springs, swales, shores, ditches. 800–2700 m. BR, BW, ECas, Owy, Sisk. CA, NV, ID, WA; north to British Columbia, east to SD, southeast to NM. Native.

This species is often confused with Juncus occidentalis, which shares the brown-striped tepals and crested capsules but does not grow east of the Cascades. Where they overlap in southwestern Oregon and California, they are separable by the internal structure of the capsules: three-chambered in J. confusus and one-chambered in J. occidentalis.

River shores. 50–200 m. Col. CA, ID, WA; throughout North America. Native.

Source

Flora of Oregon, volume 1, page 274
Peter Zika

Flora of Oregon, volume 1, page 279
Peter Zika

Sibling taxa